Cellulase preparation derived from Trichoderma viride was chromatographed in one step by a column. The fraction which had cellulase activity (PEAK I) had little P-glucosidase activity. PEAK I was used for continuous hydrolysis of MCC. Holding PEAK I (3.0 g/l) in a reactor and supplying MCC suspension (12.8 mg/h) into a reactor continuously, the hydrolysis of MCC in a reactor was performed. As the result, during the steady state from 168 h to 576 h, the concentration of cellobiose in a reactor is about 3.5 to 3.0 g/l, the content ratio of cellobiose in reaction solution collected, 75%, and the ratio of cellobiose to glucose, 3.0. Moreover. the yield of cellobiose is 60%. All these values are considerably high, compared with the experimental value in the previous paper. The system of continuous MCC hydrolysis ill this paper has two main merits. in that the hydrolysis of cellobiose to glucose is prevented because the reaction products are taken out of the reactor continuously, and the loss of enzyme is low because inactivation of the enzyme hardly occurrs during the reaction.